The present invention relates to a system for cooling a box comprising electronic devices and more particularly to a fan with self closing blades for, in case of failure, preventing air leakage in a box comprising a plurality of fans.
In many electronic systems, the electronic cards are cooled by air. An air flow goes through the electronic cards, and thus cools down the electronic components situated on the cards. This allows power dissipation in such components and maintains the silicon temperature of such electronic components (in particular semiconductor chips) to a value compatible with specifications.
The common implementation of a cooling system in a large computer or telecommunication system comprising a plurality of electronic devices is to arrange an array of fans (blowers, ventilators) controlled by a servo mechanism capable of detecting over temperature conditions, lack of fresh air, air renewal deficiency, defective air circulation, fan failures or malfunctions, and capable of adjusting the speed of these fans to actual conditions. Generally, an additional blowing capacity in large electronic systems is required for, in case of fan failure, replacing the air flow that was previously generated by the failing fan, and providing an additional air flow to compensate for the air leakage through the failing fan.
This implies complex sensors, powerful amplification for fan servo control, and backup fans for replacing the failing fan. A solution for reducing the air leakage through the failing fan and to limit the additional blowing capacity required is to add a mechanism on top of each fan to close the fan opening in case of failure.
UK Patent Application 2 081 878 A and U.S. Pat. No. 4,590,889, the disclosures of which are incorporated by reference herein, disclose ventilation arrangements with pivotable blades for closing the opening of a ventilation duct.
More particularly, UK Patent Application 2 081 878 A entitled xe2x80x9cVentilatorsxe2x80x9d (Bardsley) discloses a ventilation apparatus adapted to combine the operating features of an air extract system and a recirculation system comprising a number of pivoted blades or shutters mounted over openings in the sides of a vertical exhaust duct. Below the opening is mounted a reversible air flow fan. When the fan is blowing air up, the blades are blown open, to allow air to pass up the duct, at the same time the blades also close the openings in the sides of the duct. When the fan is off, the blades, due to their slight imbalance fall down onto a stop within the duct to hold the blades in a horizontal position forming a xe2x80x9cback-draughtxe2x80x9d shutter. When the fan is reversed and blowing down, the blades remain in their horizontal position and air is drawn through the openings in the duct and discharged down by the fan.
U.S. Pat. No. 4,590,889 entitled xe2x80x9cArrangement for Influencing a Cooling Air Flowxe2x80x9d (Hiereth) discloses an arrangement for influencing a cooling air flow passing through a cooling air system of an internal-combustion engine of a vehicle including a heat exchanger and a blower arranged in an air guiding housing, a cooling air outlet opening being arranged in the air guiding housing between the blower and a wall of an internal-combustion engine capsule in the area of the bottom side of the vehicle. In order to achieve a better efficiency of the blower and in order to prevent the emission of sounds from the ventilated capsule, pivotable guide blades are arranged in flow direction in front of and/or behind the running blades of the blower which, as a function of the position, closes the cooling air inlet opening to the capsule and opens the cooling air outlet opening arranged in the air guiding space between the heat exchanger and the blower.
None of these documents approaches the problem of closing the a opening of a failing fan for reducing air leakage in a box or enclosure comprising a plurality of fans.
It is an object of the present invention to limit the additional blowing capacity required to cool a box comprising electronic devices in case of fan failure.
It is a further object of the present invention to limit the air leakage generated by a failing fan.
It is a further object of the present invention to close the opening of a failing fan whatever the position, horizontal or vertical, of the box.
It is a further object of the present invention to simplify the air cooling in a box comprising a plurality of fans.
The present invention relates to a system for cooling a box comprising electronic devices and more particularly to a fan with self closing blades for, in case of failure, preventing air leakage in a box comprising a plurality of fans.
The present invention is directed to a fan system to be mounted over an opening and comprising a plurality of pivoting blades fixed on a central rotating element. The fan system comprises:
a central rotating element and means for automatically closing the opening with the surface of the blades when the fan is stopped, comprising means for pivoting each blade around an axis fixed on the central rotating element from an open to a closed position; means for automatically placing blades in a blowing position when the fan is running, comprising means for pivoting each blade around an axis fixed on the central rotating element from a closed position to a blowing position.
The fan system further comprises at least one fan to be mounted over an opening comprising:
a motor driven element having first stops;
a free wheeling element;
a plurality of pivoting blades fixed on the free wheeling element; and
resilient members fixed on the free wheeling element wherein, in operation, when the fan is operating and the motor driven element is engaged, the first stops push the pivoting blades to a first, blowing position, and when the fan is not operating, the resilient members push the pivoting blades to a second , closed position.
The fan system further comprises:
a motor driven element comprising means for rotating the blades and for pivoting the blades from the closed to the blowing position.
The central rotating element is a free wheeling element comprising for each blade:
means for positioning each blade in the closed position;
means for positioning each blade in the open position; and
means for pivoting each blade from the blowing to the closed position.